The present invention relates to a plasma processing apparatus using microwave, and in particular to a plasma processing apparatus using microwave suitable for feeding stably plasma with microwave electric power.
The density of current flowing through wiring increases with progressing fineness and increasing density of LSIs, which is a problem with regard to realization of LSIs of next generation. For this reason research for forming a wiring film of high quality is in progress and the bias sputtering method is one of the methods useful for forming high quality films. The bias sputtering method is one for forming a film while irradiating a substrate, on which the film is to be formed (hereinbelow called simply substrate) with ions, by which it is possible to control the crystallinity of the film by irradiation with ions and to improve the coverage of steps by the film. However, by an actual sputtering apparatus, since the generation of the plasma and the sputtering of a target are effected simultaneously only by DC or high frequency electric power, it is difficult to control the amount of ions projected to the substrate, contrarily to the fact that the energy thereof can be easily controlled by giving the substrate a bias voltage. Therefore a sputtering film forming apparatus using microwave as a second energy source has been developed.
When microwave is used, it is possible to generate a high density plasma in a high vacuum region and to control the quantity of ions by varying the microwave electric power, independently of the DC or high frequency applied to the target. For this reason attention is paid thereto.
Heretofore an example, in which microwave is used for forming a conductive film, is proposed e.g. in JP-A-59-47728 (related to U.S. Pat. No. 4,492,620).
The prior art technique described above has a problem that film forming processing cannot be performed for a long time, because metallic material, with which the film is to be formed, is attached to the surface of the part made of dielectric material for introducing microwave (hereinbelow called window material), which hinder the transmission of the microwave.